Field of the Invention
The present invention relates to an image sensor and an electronic device using the same.
Description of the Related Art
In an image sensor such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor, generally, as the area of the photoelectric conversion portion of a pixel becomes large, the light receiving amount increases, and the S/N ratio improves. However, since a plurality of control transistors are formed in the periphery of the photoelectric conversion portion of the pixel, the light receiving area per unit pixel cannot be increased. Additionally, in an imaging apparatus such as a digital camera or a digital video camera, when the number of pixels of the image sensor is increased to shoot a high-resolution image, the light receiving area per unit pixel reduces. For this reason, the image quality may degrade because the S/N ratio lowers.
On the other hand, a stacked image sensor has been proposed recently in which two semiconductor chips, that is, a CMOS image sensor chip and a signal processing chip are integrated into one package. For example, Japanese Patent Laid-Open No. 2010-225927 proposes an image sensor in which a pixel including a photodiode and a plurality of control transistors is formed on a first chip, and a driving circuit for driving the pixel is formed on a second chip.